Arteriole

An arteriole is a small artery that carries blood toward capillary beds. Its muscular wall can change vessel diameter, regulating local blood flow and contributing to blood pressure.

Vascular smooth muscle: Involuntary muscle cells in blood vessel walls that contract or relax to change vessel diameter. Its contraction narrows arterioles; relaxation widens them.
Autoregulation of blood flow: The ability of an organ to maintain relatively stable blood flow despite changes in perfusion pressure. Arterioles adjust their diameter to preserve perfusion within organs.
Artery: A blood vessel that carries blood away from the heart. Arterioles are the small downstream branches of arteries.
Metarteriole: A small vessel linking an arteriole to a capillary bed in some microvascular descriptions. It is a transitional pathway between arteriolar inflow and capillary exchange.
Vasoconstriction: Narrowing of a blood vessel caused by contraction of its smooth muscle. Arteriolar vasoconstriction increases resistance and reduces downstream flow.
Cerebral autoregulation: The regulation that keeps brain blood flow relatively stable across a range of arterial pressures. Cerebral arterioles change tone to protect brain perfusion from pressure fluctuations.
Capillary: A microscopic blood vessel with a thin wall where gases, nutrients, and wastes exchange with tissues. Arterioles deliver blood to capillary networks.
Venule: A small vessel that collects blood from capillaries and carries it toward veins. Venules receive blood after it passes through capillary beds supplied by arterioles.
Vasodilation: Widening of a blood vessel caused by relaxation of its smooth muscle. Arteriolar vasodilation lowers resistance and can increase tissue perfusion.
Renal autoregulation: Kidney mechanisms that stabilize renal blood flow and filtration as arterial pressure varies. Afferent arterioles alter resistance to help stabilize glomerular filtration.

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PericyteRelated: Pericytes occur near the transition from arterioles to capillaries, where vessel cell types can overlap.